Heretofore, there has been known a construction machine provided with a base frame which supports a working attachment so as to be raised and lowered, an engine installed on the base frame, and a guard panel for covering over the base frame.
In construction machines of this type it has recently been desired that an exhaust gas after-treatment device for purifying exhaust gas from an engine be installed on a base frame.
More particularly, the aforesaid exhaust gas after-treatment device has a DPF (Diesel Particulate Filter) for decreasing the amount of dust such as soot and mist contained in the engine exhaust gas and also has a reduction catalyst for decreasing the amount of NOx contained in the exhaust gas (see, for example, Patent Documents 1 and 2).
However, since the engine and related peripheral devices (e.g., hydraulic systems) are disposed in a planarly massed layout on the base frame, it is difficult to newly ensure on the base frame a space as a planar space for disposing the exhaust gas after-treatment device.
One countermeasure is to ensure a new space over the base frame. However, with a mere installation of the exhaust gas after-treatment device over the engine and a peripheral device thereof, not only the construction machine itself becomes larger in height, but also there results the problem that the visual field from the operator becomes narrow.    [Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-90214    [Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-120277